Conventionally, a tubular-member lock mechanism has a structure of switching a lock position and a release position of a lock-mechanism main member and a tubular member by rotationally operating a fastener (lock member) attached to the lock-mechanism main member.
For example, a tubular-member lock mechanism as shown in Patent Document 1 comprises a fastener (lock member) formed by a locking arm made of an elastic member and mounted to a vicinity of a notch groove of a female pipe (lock-mechanism main member), and a fastener projecting portion, and has a structure wherein the tubular member is locked by the fastener entered from the notch groove of the female pipe, and is released by pushing the projecting portion of the fastener to turn so that the locking arm opens to disengage from the tubular member.
In the fastener (lock member), at the lock position, the locking arm of the fastener protrudes radially inwardly from the notch groove to retain the tubular member.
Also, at the release position, the projecting portion turns so that the locking arm opens as an operation point of an end portion of the notch groove, and moves from an inside of the female pipe in an opening direction so as to be disengaged from the tubular member (Patent Document 1).